For about eight decades, the 258-foot Melvale Gas Holder has towered above northern Baltimore. In seven seconds Sunday morning, the storage tank will be brought to the ground.

BGE plans to implode the steel structure, which hasn't been used since 1997. Preparations for the implosion have taken months, and demolition experts have been working at the site near the Jones Falls Expressway and Cold Spring Lane for about four weeks to set up.

The implosion will take place as soon after 7 a.m. as possible, BGE officials said.

On Saturday, workers from Controlled Demolition Inc.finished rigging the system that will bring down the structure, said Thom Doud, project manager for the company. About 420 charges filled with the explosive RDX have been placed in more than 160 locations on the structure, he said. A small amount of dynamite — about 4 pounds — also will be used.

Officials have not designated a public viewing area and say it will be hard to see the implosion because of road closures around the 26-acre site. BGE is encouraging people to watch the event on local TV broadcasts rather than try to see it in person; several stations planned to carry it.

Rain made for a muddy work site Saturday but otherwise did not interfere with preparations. Fog is the only weather condition that would pose a problem Sunday, because it can amplify noise and affect air pressure, increasing chances of damage outside the site, such as broken windows, Doud said.

Doud — the man who will push the two buttons to trigger the implosion sequence — said people can expect a loud noise, some smoke and a small amount of vibration.

"We're expecting no more vibration that you would get from a tractor-trailer driving by your house," Doud said.

How far the sound carries will depend on wind direction and velocity.

"Noise actually travels with the wind," he said.

Eleven seismographs — machines that measure vibration and noise — have been set up to monitor vibrations around the site, he said.

CDI is based in Baltimore County's Phoenix area and has demolished structures around the world, including casinos in Las Vegas, the Seattle Kingdome and the portion of the Alfred P. Murrah Federal Building that remained after the Oklahoma City bombing in 1995.

Before demolition crews arrived, environmental remediation included the removal of oils and tar, said Steve Stultz, project manager for BGE. The structure was also pressure washed.

Potts & Callahan will cut up and recycle the steel, with cleanup expected to take about two months, said Tim Collison, the contractor's executive vice president.

The gas holder was built in 1933, when manufactured gas was used. It does not have updated technology for today's natural gas, Stultz said.

Maintenance has become too costly for the obsolete building, BGE spokesman Rob Gould said

"To maintain this facility is not in the best interest of the customer," he said. "At the end of the day, it just makes little sense to maintain the facility using customer dollars."

Roads around the site, including the Jones Falls Expressway and Cold Spring Lane, will be closed briefly for the implosion, city transportation officials said.

The company has not decided how to use the site in the future, Gould said. The city's new Jones Falls hiking and biking trail will go through the property.